The present invention relates to a novel resin composition having excellent impact strength and good heat and chemical resistance and moldability. More particularly, it relates to a resin composition which comprises a polyamide, a polyarylate, a butadiene copolymer obtained by an addition of an unsaturated dicarboxylic acid anhydride, and an epoxy group-containing olefin copolymer.
The resin composition of the present invention is expected to be used for automobile parts, particularly exterior plates or external parts of automobiles and for general mechanical parts, by virtue of its excellent impact resistance, chemical resistance, heat resistance and moldability.
A resin composition comprising a polyarylate and a polyamide, or a polyarylate, a polyamide and a polyester, is known. For example, Japanese Examined Patent Publication No. 50260/1983 discloses the properties of a three component resin composition comprising a polyarylate, a polyamide, and a polyester or a polyesterether.
Further, the Japanese Unexamined Patent Publications No. 100552/1977 and No. 100553/1977 disclose processes for its production. The Japanese Unexamined Patent Publication No. 94366/1978 discloses a method for imparting flame retardancy thereto.
A resin composition comprising a polyarylate and a polyamide (if necessary, further containing a polyester or a polyesterether) is excellent not only in chemical resistance and heat resistance, but also in moldability, and it is used primarily in electric and electronic applications. The polyarylate obtainable from bisphenol A and a phthalic acid mixture comprising terephthalic acid and isophthalic acid, has excellent heat resistance, but as is well known, its chemical resistance is not adequate and environmental stress cracks are likely to form. Further, its moldability is not good. On the other hand, a resin composition comprising 30% by weight of this polyarylate, 50% by weight of nylon 6 and 20% by weight of a polyethylene terephthalate, has excellent chemical resistance, and its heat distortion temperature is also high at a level of 160.degree. C. The moldability is about ten times superior to the polyarylate alone, as evaluated by a spiral flow test. By virtue of such properties, this resin composition is widely used in electric and electronic applications.
However, the impact strength of the resin composition comprising a polyarylate and a polyamide (optionally further containing a polyester or a polyesterether) is not necessarily adequate. For instance, in the case of a resin composition comprising 50% by weight of a polyarylate and 50% by weight of nylon 6, the Izod impact strength is 7 kg.cm/cm, which is relatively low for an engineering plastic. Therefore, its use has been rather limited. For example, when the resin composition is used for an external plate or exterior part of an automobile, the Izod impact strength is required to be at least 20 kg.cm/cm. Under these circumstances, the application of said resin to an external plate or exterior part of an automobile has been hindered by the inadequate impact resistance in spite of the excellent chemical resistance, heat resistance and moldability. Therefore, it has been expected that if the impact resistance of said resin composition can be improved, its application will remarkably expand not only in the field of external plates and exterior parts for automobiles but also in other fields.
In an attempt to improve the impact resistance of said resin composition, it has been proposed to incorporate either an elastomer in Japanese Unexamined patent Publication No. 56652/1979, an ionomer in Japanese Unexamined Patent Publication No. 93043/1974, a sulfonic acid group-containing polyethylene terephthlate in Japanese Unexamined Patent Publication No. 105050/1984 or an olefin copolymer of a glycidyl ester of an .alpha., .beta.-unsaturated acid in Japanese Unexamined Patent Publication No. 183353/1986.
Further, the present inventors have proposed to incorporate an epoxy group-containing olefin copolymer and an acid anhydride-containing olefin copolymer in the specifications of Japanese Patent Applications No. 119585/1986 and No. 127063/1986.
Such a resin composition comprising a polyamide, a polyarylate, and a toughness imparting material, and having excellent impact strength, heat resistance, and moldability, is expected to be useful for exterior plates and external parts of automobiles or the like.
Further, in such fields of application, cost for materials of the resin composition are an important problem in addition to the physical properties of the resin composition, and many attempts to reduce the costs for materials have been made. In a resin composition comprising a polyamide, a polyarylate, and a toughness imparting material, the polyarylate is relatively expensive. Therefore, in order to reduce the costs for materials of the resin compositions, it is necessary to reduce the blending ratio of the polyarylate or to replace part of the polyarylate with other relatively cheap materials.
However, if the blending ratio of the polyarylate is reduced, the deterioration of heat resistance is substantial, and if a part of the polyarylate is replaced with an ABS resin or a polyethylene terephthalate, the deterioration of impact resistance is substantial.